Control of electron discharge device of area selection type



Aug. 15, 1950 G. w. BROWN CONTROL OF ELECTRON DISCHARGE DEVICES FOR AREASELECTION TYPE 2 Sheets-Sheet 1 Filed Aug. 30, 1946 617/0 Mfr/l(Ittotneg Aug. 15, 1950 e. w. BROWN CONTROL OF ELECTRON DISCHARGEDEVICES FOR AREA SELECTIONTYPE Filed Aug. 30. 1946 2 Sheets-Sheet 2trill/I467 l/l/lllllllllIl/lIl/l/lIl/lIl/lllIl/lIl/l/lllll/nnnnnunnnnnnnnn 3nnentor fiearge Bma'm (Ittomeg iatented Aug. 15, 1950UNITED STATS CONTROL OF ELECTRON DISCHARGE DEVICE F AREA SELECTION TYPEGeorge W. Brown, Cranbury, N. J., assignor to Radio Corporation ofAmerica, a corporation of Delaware Application August 30, 1946, SerialNo. 694,041

8 Claims. (Cl. 250-275) This invention relates to electron dischargedevices of the area selection type which employ a plurality of angularlyrelated grid wires which are adapted to be individually energized so asto open and close selected apertures to control the passage ofelectrons. A co-pending application of J. A. Rajchman, Serial No.665,031, filed April 26, 1946, now Patent No. 2,494,670, issued January1'7, 1950, for improvements in Electron Discharge Devices, describes andclaims a discharge device of this type which has the ability to selectinstantly any one of a very large number of apertures, and thus tocontrol the particular area on a target electrode which is impinged byelectrons.

The co-pending application of J. A. Rajchman referred to above describesvarious forms of and uses for the area selection tube. One of the moreimportant uses resides in its ability to store or remember informationin connection with electronic computing devices. The primary purpose ofthe present invention is to provide an improved method ofinterconnecting the grid wires so as to control a very large number ofapertures or windows with a minimum number of external leads fromthetube and a minimum quantity of control circuits. Consequently, thespecification and drawings of the Rajchman application are embodiedherein by reference.

From an operational point of view, there are two basic types of controlwhich may be utilized in the area selection tube, alternatively, (a)deflection and (b) potential barrier. The former comprises a cathode ofconventional construction and a gridmesh which consists of two gridnetworks, each comprising a plurality of spaced, parallel grid wires,the wires of both networks being substantially perpendicular to the pathof the electrons while being mutually at an angle one with respect tothe other so as to form windows through which electrons may pass to thetarget electrode. The target electrode may comprise a dielectric surfaceand such other elements as are necessary to form a memory element, or afluorescent screen may be utilized, or a combination of both. The gridwires of each network, which may, for example, be disposed horizontallyand vertically, respectively, should be shaped and/or spaced so that thedepth of the passageway between adjacent wires, measured along theelectron axis, is at least twice the distance between the wires. In oneform, the wires may be rectangular in shape to fulfill this requirement.It was shown that if a negative potential is applied to all grid wires,electrons will be repelled and none will pass through the grid. If onewire is made positive by 100 volts, say, electrons in the vicinity willbe attracted to it, but none will pass through the g i Howev r, if twoadjacent grid wires are made positive, then electrons will beaccelerated towards and pass between those two wires. One adjacent,horizontal pair and one adjacent, vertical pair of wires can thus beconsidered as forming a window through which electrons will pass onlywhen all four wires are positive.

The potential barrier type of construction utilizes a cathode, a firstaccelerating grid near the cathode, a second accelerating grid justahead of the control grid, a control grid and a suitable targetelectrode. The second accelerating grid consists of a plurality of wiresequal in number to and in register with the wires of the adjacentcontrol grid network. Thus, if the control grid network nearest thecathode consists of a plurality of wires parallel to the axis of thecathode, or vertically arranged, then the accelerating grid wires wouldbe parallel thereto and, of course, at right angles to the horizontalgrid wires of the second control grid network. All of the wires of eachaccelerating grid are connected together and suitable positivepotentials applied thereto, say volts. As before, the wires of thecontrol grid networks are adapted to be individually biased with eitheone of two voltages to open and close selected windows. In the presentcase, a window will be closed to the passage Of electrons if any one ofthe four grid wires defining it is biased to a negative potential of,say, 100 volts. To open a window, all four wires must be at cathodepotential.

The present invention is not concerned with the shape or arrangement ofthe tube and is utilizable with either the potential barrier ordeflection types of control. Many modifications will be apparent,including those described in the co-pending application referred toabove. For some purposes, the grid and target electrodes may lie inparallel planes, or perhaps in parallel segments of a cylinder. In othercases, a complete cylindrical form may be preferred in which the gridwires of one network are parallel to and equidistant from the centralcathode and the other wires are circular, or where the networks areformed by wires which spiral in a right- "handed and left-handedfashion, respectively, about the cathode. It will be appreciated,however, that in all cases, the number of windows available, and hencethe definition of the grid, is equal to the product of the numbe ofwires in one grid network multiplied by the number of wires in the othergrid network. When the particular requirement is satisfied by arelatively small number of windows, no particular problem is involved inconnecting the grid wires individually to controlled sources ofpotential. However, when economy of design demands the largest possiblenumber of windows, say a million, it would be entirely impractical tobring out from the tube two thousand lead wires, one thousand Zero andone.

for each grid network. Such a large number of discrete controlpossibilities is entirely practical and provides, for example, nearlyunlimited design of computers wherethe tube is used as a memory device,or where the fluorescent screen trace produced by the successiveopeningof. different windows requires a high degree of defiiii-' tion.

Because the passage of electronsthrough a given grid network iscontrolled by the application of suitable voltages to two adjacentwires, certairr combinatorial arrangements are possible. That is, ifcertain grid wires of a network are interconnected permanently withinthe tube so that when two adjacent; grid wires are energized to allowelectrons to pass the other grid wires cerinected to them do not lieadjacent to one another in any instance, then individual control oar istill be exercised and the number of leads can be greatly reduced. Theso called Binary system described and claimed by Rajchman accomplishesthis result but it requires more than one grid mesh disposed for thesuccessive selection of areas. For example, a tube having 4,096 windowsrequires three horizontal and three vertical grid net-work's, eachhaving 64 wires. Each network is to interconnected that any quarter ofits area may be opened, the second network selecting a quarter of thefirst open. area, and the third selecting a quarter of the remainingarea; which is the one desired window.- The external leads are groupedin pairs and are energized in push-pull; This system is. ideally suitedfor" use with the Binary counting system since all numbers,- as weordinarily know them, are reeresentes by combinations of two numbers,zero can then conveniently be 1*- presented the condition in which thefirst wire of each pair is positive with respect to the second, andfleneby the opposite condition. However; not all uses of the tube utilize theB" cry counting system and the requirement. for e than two grid networksimposes a great amenity or eensnnetion since all the wires of eachsimilar and netwerk must be accurately in register. It is; therefore, afurther purpose or this ion to overcame the disadvantages of the easystem and to provide combinatorial arrangements which do not requiremore than two grid network's, one horizontal and one Vermeer-er theequivalent.

It is a further obj'e'et of this invention to provide animproved areaselection tube.

A still further object of this invention is to provide means for and amethod of interconnecting a plurality of grid wires so as to control thepassage of electrons to a selected 51301? or area of a target.

A further object of this invention is to provide means for controllingindividually the opening of one of a plurality of windows foriiied bythe intrseetio'ii's of the grid wires of a pair or grid networks whileutilizing a. number of connected leads substantially less than thenumber of wires iii each network.

A still further object is to control the perm of impact of electrons toselected areas of a target electrode while employing a of control leadswhich is substantially less than the --ber of areas available forselection.

sdiacent two "of a mommy or 'g'rid wires,

utilizing a number of connecting leads less than the numberof gridwires.

A still further object is to provide, in a disdevice having only twoassociated netwerks of grid wires, which control the passage ofelectrons therethrough, means for applying a selected. voltage to anytwo selected adjacent grid wires in each network but not at the sametime to any other adjacent grid wires by means of lead wires less innumber than the total number of wires said networks.

The riovel features that are considered characteristic of this inventionare set forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation, aswell as additional objects and advantages thereof, will best beunderstood fromthe following description of several embodiments thereof,when read in corinection with the accompanying drawings, in

which: I

Figure 1 represents a grid mesh connected in accordance with the Groupof One system;

Figure 2 represents a grid mesh connected in accordance with the Groupof Two system; and

Figures 3 and 4 are sectional views of a preferred embodiment of thisinvention.

There are two related systems which may be employed in carrying outthisinvention. The first of these is herein called the Group of One systemSince for each grid network there is one group of leads, any two ofwhich may be energized to open just one gate, where a gate is thepassageway between adjacent wires of a single network. Thesecond iscalled the Group of Two, since the leads to a given network aredivided'in-to two groups having the same or difierent numbers of leadsin each group. In this case, a single gate is opened by the applicationof suitable voltages to a lead in each group.

Group of One Considering a typical Group of one system first; referenceis madeto Fig 1, illustrates dia'g mniatically an interconnected gridmesh with the dash line I, comprising a first grid network 3 of 21-horizontal grid wires and a seec ind grid network 5 of 21 verticalwires.- Within the tube,- connections are made from the wires ornetworks 3 and 5 to a group of seven leads I and 9 which are broughtthrough the glass envelop'e in any convenient manner.

For convenience of illustration, the two grid networks have been shownas lying in spaced parallel planes, but it is to be understood that anyof the physical arrangements deseribed above or which conform to thefunctional requirement set forth ma be einployed= It is also to beunderstood that each grid wire is insulated from every other grid wire,connections to the leads being indicated by a heavy dot on theintersection of the lines representing the respective elements. since apreferred form of construction is a helical arrangement in which thefirst wire is adjacent the last wire and is paired with it to form oneof the gates, the electrical equivalent of this has 5. shown'will'require one additional wire for each network.

Since the two networks and their connected leads are identical, it willsuffice to limit the detailed description to one of the networks.

Remembering that the object of interconnecting the leads 9 with thewires is to make certain that when an opening voltage is applied to anytwo leads, there will be one and only one pair of adjacent wiresconnected to those leads, one of the many possible combinations isillustrated by the heavy dots on the intersections of the lines. Readingfrom left to right for the network wires and down for the lead wires, itwill be observed that the first seven wires are connected to the firstseven leads; the eighth to eleventh wires connect to leads I, 3, 5 andI; the twelfth to'iourteenth wires connect to leads 2, 4 and 6; thefifteenth to seventeenth wires connect to leads I, 4 and I; theeighteenth and nineteenth wires connect to wires 3 and 5; and wires 20and 21 connect to leads 2 and 6, all respectively. It may be observedthat whatever two leads are selected, one and only one pair of adjacentgrid wires can be found connected to them.

It will be observed also that in each network there are twenty-one gatescontrolled by seven leads. When n is the number of leads, and when n isodd, there are possible different pairs or combinations which may bemade. Obviously, when 11:7, there are twenty-one possible combinations,and, therefore, the arrangement shown provides the most complete andefficient use of the grid. Thus, in the Group of One system, with anyodd number 11. leads connected to a given grid network, the maximumnumber of gates or the selecting power of the grid is one out of Theselecting power of the complete grid mesh is, of course, determined bythe product of the gates in the cooperating grid networks, and in thepresent case is 1 out of 21 or 441. Therefore, with a total of 14control leads, any one of 441 distinct incremental areas or points onthe target may be selected, and this with only one grid mesh, asdistinguished from the Binary system which, for example, with 16 leadswould require four grid networks or two meshes and would only have aselective power of one out of 256.

To illustrate the selective power of a single grid network fed by 11.lead wires, and complete grid meshes of two similar networks, considerthe following table showing typical arrangements:

From this chart it may be seen that two grid networks with 990 gridwires each connected to a total of only grid leads can control the individual selection of nearly a million windows. When used in a memoryarea selection tube, 90 electronic or mechanical switches can thuscontrol nearly a million memory-elements, so that by the selection ofall possible combinations of pairs of horizontal and vertical leads,that number of memories may be successively actuated in a single tube,the information being stored and held until needed and then taken fromthe tube in the manner fully set forth in the Rajchman application. Theequivalent tube using the Binary control method would require less leads(40), it is true, but the tube construction would be complicated by thenecessity of providing five horizontal and five vertical grid networksin register, each network having over 1024 grid wires. It must beappreciated that the particular gridto-lead connection schemeillustrated is but one of an innumerable number of ways ofinterconmeeting these elements to insure selection without duplication.To insure that no possible combination is overlooked, and to makecertain that there is no duplication, it is desirable to figure theconnections in accordance with some definite plan. The plan used above,by way of illustration, applicable to any Group of One system when thenumber of leads n is odd, is as follows:

Number the 12 leads in sequence, 1, 2, 3 11.. Write these numbers in acircle. Thus, where 11::7:

Number the grid wires in sequence,

n n-l 1, 2, 3

which in this case is 21. Connect the grid wires from 1 to 21 to thenumbered leads obtained by (a) Starting with 1, read around the circlein order, 1 to '7;

(2)) Starting with 1, take alternate numbers until all numbers haveappeared once; i. e., 1, 3, 5, 7, 2, 4, 6;

(0) Starting with 1, take every third number until all numbers haveappeared once; i. e., l, 4, 7, 3, G, 2 and 5.

Modifications of the above plan are possible without limit. For example,instead of numbering the grid wires in sequence, they may be numbered inany arbitrary order. Alternatively, or in addition, the lead wires maybe numbered in any arbitrary sequence. Also, the numbers 1 to 11 may bearranged in the circle in any arbitrary sequence. A further modificationis to start not at 1 but at any number. The essential requirement is,however, that considering any two lead wires, only one pair of adjacentgrid wires can be found connected to them.

A plan which has constructional advantages, which result from theuniformity of the connection pattern, modifies the steps ofsub-paragraphs (a) to (0) above to the following extent: Instead ofcompleting all 11 numbers by taking first every number, then everysecond and then every third, change the sequence with each step. Thatis, starting with any number on the circle, 1, for example, advance onenumber, then two numbers, then three numbers, repeating 1, 2, 3, 1, 2,3, until the cycle is completed. The step se- 7 queries may be 3. 2, 1..or sequence of the 2, l, 3, or any arbitrary numbers, as desired.

Where n is even, similar systems may be used. However, no particularadvantage is gained and there will be certain unused pairs.

Group of Two Like the Group of One, the Group of Two uses only one gridnetwork for each direction. and the method of connection is the same foreach network. The wires of each network are connected to leads dividedinto groups or families a and b as shown in Fig. 2. Thus, each networkhas a+b leads and the system a total of 2(a-l-b) leads. In operation,the opening or control voltage is always applied to one lead in eachgroup. Since it is possible to choose one group a lead and one group 1)lead a b times without duplication of pairing, it follows thateach gridnet.- Work will have a b wires and there will be a b gates and (a-Xb) 2windows controlled thereby. The greatest degree of control for a givennumber of grid wires will occur when a and b are equal. It is also clearthat each grid wire onnected to a lead of the a group must be adjacent agrid wire of the 12 group. For maxi mum ciiiciency of the use of leads,a and b should be even. While it is usually preferable, it is notessential to have the two grid networks identical.

The grid wire connections to the leads illustrated in Fig. 2 is only oneof many possible arrangements. Systems for assuring the variation of thelead sequence without repetition can be employed as in the case firstdescribed, and it is believed to be unnecessary to give further details.

For purposes of comparison, figures are given below showing a fewrepresentative combinations of design.

From the above, it can be seen that two grid networks of 1824 wireseach, connected to a total of 128 loads will control over a millionwindows or memory elements when the leads are connected in two groups.of 32 wires each.

The Group of Two system is particularly suitable for use with decimalsystem computers since with leads (a multiple of 10) ten thousandelements (a power of 10) can be controlled.

Figs. 3 and 4 illustrate the essential features oi a preferredembodiment of this invention employing two grid networks of 32 wireseach, although for simplicity of illustration every other grid wire hasbeen omitted, the missing wires being indicated by dotted lines wherethey ter minate. A central cylindrical cathode i5 is pro- Vided whichmay be indirectly heated in conventional manner. The first grid networkcon sists of 32 rectangular grid Wires ll, each wire being mounted atits extreme ends in mica supporters l9, 2! and spiraling concentricallyabout the cathode so as to be equidistant from the cathode. The pitch issuch that each wire completes a half a turn about the cathode. The wiresare uniformly spaced from each other, and bent so that the thin edge isalways perpendicular to radial lines passing through the cathode.Looking down on the top View (Fig. 3) the wires of the first networkspiral downward in a counterclockwise direction. The second grid networklies just outside the. inner network, and i concentric therewith. Eachof its wires 23. spiral in a clockwise direction. Consequently, eachwire of the first network intersects or crosses each wire of the secondnetwork when viewed from the cathode to form a complete grid mesh of1024 windows. Enclosing the grid is a. cylindrical target electrode 25which may be of various forms to comprise a dielectric memory element,fluorescent screen or both, as previously discussed. The. electrodes areall mounted within a suitable evacuated glass envelope 2'5. At one end,the necessary leads are brought out through small glass to metal seals29 as is well known. The number will be determined y the system used tointerconnect the grid wires, plus those required tor the cathode, heaterand target elec'- trodes No attempt has been made to show the internalconnections, since these have been fully explained above, the systemsbeing illustrated in Fig. 1 or 2.

There has thus been described an improved area selection tubecharacterized by its high elective p w r, w th a minimum number ofexternal le ds and a single rid.

I claim as my invention:

1.. In an electron discharge device having a plurality of. grid wiresfor controlling the passage of electrons between a Selected pair ofadjacent wires by the application of the. same, predatormined potentialto said adjacent wires, 2, plurality of leads affording externalconnection to said grid wires, each lead being connected to more thanone grid wire, there being n leads and n(n-l) 2 grid wires controlledthereby.

2. An electron discharge device having a cathode, a target and a controlgrid positioned between said first named elements, said Control gridcomprising two grid networks which cooperate to define windows throughwhich electrons may pass to strike a selected area of said target onlywhen two adjacent grid wires of each network are energized with the samepredetermined potential, a plurality of leads for each network, saidleads being substantially less in number than the numher of grid wiresin the associated network, and connections between each of said leadsand selected ones of said grid wires whereby the application of saidpredetermined potential to a given pair of leads for each network causessaid potential to be applied to one and only one adjacent pair of wiresin each network.

3. A device of the character described in claim 2 in which n leadscontrol the unique application of potentials to L lli 2 grid wires, ineach network.

4. An electron discharge device, comprising a source of electrons, atarget, grid means intermediate said source and said target forcontrolling selectively the flow of electrons from said source todistinct incremental areas of said target through electron windowsformed by an adjacent pair of grid wires in a first network and an adjacent pair of grid wires in a second network at an angle thereto, aplurality of leads for each network for applying controlling potentialsto said pairs of grid wires so as to open and close said windowsindividually and thereby control the flow of electrons, said leads andsaid grid wires being interconnected so that the application of controlpotentials to a selected pair of leads for each entwork permits windowsto be individually controlled, where n is the number of leads for eachnetwork.

5. A device of the character described in claim 4 in which the wires ofone network form a right hand spiral on the surface of a cylinderconcentric with said source of electrons and the wires of the othernetwork form a left hand spiral on the surface of a cylinder ofdifferent diameter concentric with said source of electrons, each wireof one network intersecting each wire of the other network.

6. A device of the character described in claim 4 in which the leads foreach of said networks are divided into two groups, control beingeffected by the selection of one lead from each group.

7. An electron discharge device comprising a cathode, a target electrodeand a grid intermediate said cathode and said target, said gridcomprising two grid networks each having a plurality of grid wires whichcooperate to define windows through which electrons may pass to strike aselected incremental area of said target only when two adjacent gridwires of each network are energized with a predetermined potential, aplurality of lead wires for each network, the number of lead wires beingsubstantially less than the number of grid wires, and connectionsbetween said lead wires and one or more of said grid wires, saidconnections providing that in each network each pair of lead wires isconnected to one and only one adjacent pair of grid wires.

8. An electron discharge device comprising a cathode, a target electrodeand a grid intermediate said cathode and said target, said gridcomprising two grid networks each having a plurality of grid wires whichcooperate to define windows through which electrons may pass to strike aselected incremental area of said target only when two adjacent gridwires of each network are energized with a predetermined potential, aplurality of lead Wires for each network, said lead Wires for eachnetwork being divided in two groups, the number of lead wires for eachnetwork being substantially less than the number of grid wires in thatnetwork, connections between said lead wires and one or more grid wiresof the associated network. said connections providing that in eachnetwork, each pair of lead wires comprising one lead from each group, isconnected to one and only one adjacent pair of grid wires.

GEORGE W. BROWN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,946,223 Mason Feb. 6, 19342,000,379 Deisch May 7, 1935 2,122,102 Lundell June 28, 1938 2,155,471Cawley Apr. 25, 1939 2,172,859 Toulon Sept. 12, 1939 2,182,152 HullegardDec. 5. 1939

